IfcCurveBoundedPlane是一个参数化平面曲面，曲面边界由一条或多条边界曲线定义。有界平面定义为从边界上任何点沿nxt方向的基曲面部分，其中N是曲面法线，T是该点的边界曲线切线向量。如此定义的区域应呈弧形连接。
基本面是一个自行建立位置坐标系的IfcPlane\表面。位置. 外边界和内边界（如提供）应位于IFC板表面。外边界和内边界曲线应使用基本面参数化提供的u和v值作为其x和y坐标值进行定义。
注：与ISO 10303-42中定义的曲线边界曲面类似的实体。
IFC1.5中增加的新实体
IFC2x 修改属性OuterBoundary和innerBoundary的数据类型已从Ifc2DCompositeCurve更改为超类型IfcCurve。
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| 1 | BasisSurface | IfcPlane | [1:1] | The surface to be bound. | X |
| 2 | OuterBoundary | IfcCurve | [1:1] | The outer boundary of the surface. | X |
| 3 | InnerBoundaries | IfcCurve | S[0:?] | An optional set of inner boundaries. They shall not intersect each other or the outer boundary. | X |
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcRepresentationItem | |||||
| LayerAssignment | IfcPresentationLayerAssignment @AssignedItems |
S[0:1] | Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items. | X | |
| StyledByItem | IfcStyledItem @Item |
S[0:1] | Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve. | X | |
| IfcGeometricRepresentationItem | |||||
| IfcSurface | |||||
| Dim :=3 |
IfcDimensionCount | [1:1] | The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item. | X | |
| IfcBoundedSurface | |||||
| IfcCurveBoundedPlane | |||||
| 1 | BasisSurface | IfcPlane | [1:1] | The surface to be bound. | X |
| 2 | OuterBoundary | IfcCurve | [1:1] | The outer boundary of the surface. | X |
| 3 | InnerBoundaries | IfcCurve | S[0:?] | An optional set of inner boundaries. They shall not intersect each other or the outer boundary. | X |
EXPRESS Specification
ENTITY IfcCurveBoundedPlane
SUBTYPE OF (IfcBoundedSurface);
BasisSurface : IfcPlane;
OuterBoundary : IfcCurve;
InnerBoundaries : SET OF IfcCurve;
END_ENTITY;
原文：https://www.cnblogs.com/herd/p/13933685.html